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Amniotic Fluid Problems: Hydramnios and Oligohydramnios

What is amniotic fluid?

Amniotic fluid is an important part of pregnancy and fetal development. This watery fluid is inside a casing called the amniotic membrane (or sac) and fluid surrounds the fetus throughout pregnancy. Normal amounts may vary, but, generally, women carry about 500 to 1000 ml of amniotic fluid. Amniotic fluid helps protect and cushion the fetus and plays an important role in the development of many of the fetal organs including the lungs, kidneys, and gastrointestinal tract. Fluid is produced by the fetal lungs and kidneys. It is taken up with fetal swallowing and sent across the placenta to the mother's circulation. Too much or too little amniotic fluid is linked to problems in development and pregnancy complications. Differences in the amount of fluid may be the cause or the result of the problem.

What is hydramnios?

Hydramnios is a condition in which there is too much amniotic fluid around the fetus. It occurs in about 1% of all pregnancies. It is also called polyhydramnios.

What causes hydramnios?

There are several causes of hydramnios. Generally, either too much fluid is being produced or there is a problem with the fluid being taken up, or both. Factors that are associated with hydramnios include the following:

Maternal factors:

Diabetes

Fetal factors:

Gastrointestinal abnormalities that block the passage of fluid

Abnormal swallowing due to problems with the central nervous system or chromosomal abnormalities

Twin-to-twin transfusion syndrome

Heart failure

Congenital infection (acquired in pregnancy)

Why is hydramnios a concern?

Too much amniotic fluid can cause the mother's uterus to become overdistended and may lead to preterm labor or premature rupture of membranes (the amniotic sac). Hydramnios is also associated with birth defects in the fetus. When the amniotic sac ruptures, large amounts of fluid leaving the uterus may increase the risk of placental abruption (early detachment of the placenta) or umbilical cord prolapse (when the cord falls down through the cervical opening) where it may be compressed.

What are the symptoms of hydramnios?

The following are the most common symptoms of hydramnios:

Rapid growth of uterus

Discomfort in the abdomen

Uterine size (fundal height) greater than expected for gestational age

Uterine contractions

The symptoms of hydramnios may look like other medical conditions. Always consult your health care provider for a diagnosis.

How is hydramnios diagnosed?

In addition to a complete medical history and a physical exam, hydramnios is usually diagnosed with ultrasound (a test using sound waves to create a picture of internal structures) by measuring pockets of fluid to estimate the total volume. In some cases, ultrasound is also helpful in finding a cause of hydramnios, such as multiple pregnancy or a birth defect.

Treatment for hydramnios

Specific treatment for hydramnios will be determined by your health care provider based on:

Your pregnancy, overall health, and medical history

Extent of the condition

How well you can handle specific medications, procedures, or therapies

Expectations for the course of the condition

Your opinion or preference

Treatment for hydramnios may include:

Closely monitoring the amount of amniotic fluid and frequent follow-up visits with the health care provider

Medication (to decrease fetal urine production)

Amnioreduction--amniocentesis (inserting a needle through the uterus and into the amniotic sac) to remove some of the amniotic fluid; this procedure may need to be repeated.

Delivery (if complications endanger the well-being of the fetus or mother, then an early delivery may be necessary)

The goal of treatment is to relieve the mother's discomfort and continue the pregnancy.

What is oligohydramnios?

Oligohydramnios is a condition in which there is too little amniotic fluid around the fetus. It occurs in about 4% of all pregnancies.

What causes oligohydramnios?

There are several causes of oligohydramnios. Generally, it is caused by conditions that prevent or reduce amniotic fluid production including:

Premature rupture of membranes (before labor)

Intrauterine growth restriction (poor fetal growth)

Post-term pregnancy

Birth defects, especially kidney and urinary tract malformations

Twin-to-twin transfusion syndrome

Why is oligohydramnios a concern?

Amniotic fluid is important in the development of fetal organs, especially the lungs. Too little fluid for long periods may cause abnormal or incomplete development of the lungs called pulmonary hypoplasia. Intrauterine growth restriction (poor fetal growth) is also associated with decreased amounts of amniotic fluid. Oligohydramnios may be a complication at delivery, increasing the risk for compression of the umbilical cord and aspiration of thick meconium (baby's first bowel movement).

What are the symptoms of oligohydramnios?

The following are the most common symptoms of oligohydramnios. However, each woman may experience symptoms differently. Symptoms may include:

Leaking of amniotic fluid when the cause is rupture of the amniotic sac

Decreased amount of amniotic fluid on ultrasound

Uterine size (fundal height) smaller than expected for gestational age

The symptoms of the oligohydramnios may resemble other medical conditions. Always consult your health care provider for a diagnosis.

How is oligohydramnios diagnosed?

In addition to a complete medical history and physical exam, a diagnosis is usually made using ultrasound. Pockets of amniotic fluid can be measured and the total amount estimated. Ultrasound can also show fetal growth, the structure of the kidneys and urinary tract, and detect urine in the fetal bladder. Doppler flow studies (a type of ultrasound used to measure blood flow) may be used to check the arteries in the kidneys, and the blood flow through the placenta.

Treatment for oligohydramnios

Specific treatment for oligohydramnios will be determined by your health care provider based on:

Your pregnancy, overall health, and medical history

Extent of the condition

How well you can handle specific medications, procedures, or therapies

Expectations for the course of the condition

Your opinion or preference

Treatment for oligohydramnios may include:

Closely monitoring the amount of amniotic fluid and frequent follow-up visits with the health care provider

Amnioinfusion--instilling a special fluid into the amniotic sac to replace lost or low levels of amniotic fluid. Amnioinfusion may be given in a woman in labor whose membranes have ruptured. Amnioinfusion will not be given if the woman is not in labor.

Delivery (if oligohydramnios endangers the well-being of the fetus, then an early delivery may be necessary)